Preparation of detergent alkylates



United States Patent 0,

3,272,881 PREPARATION OF DETERGENT ALKYLATES Brij L. Kapur and Oliver C. Kerfoot, Ponca City, Okla, assignors to Continental Oil Company, Ponca City, Okla a corporation of Oklahoma No Drawing. Filed Nov. 4, 1963, Ser. No. 321,338 6 Claims. (Cl. 260-668) This invention concerns the preparation of detergent alkylates. More particularly, the present invention relates to a method for converting diphenylalkanes obtained as a by-product in alkylating benzene with a partially chlorinated detergent range n-paraffin or mixtures thereof into monophenyl alkylates whose monosulfonate derivatives are biologically soft, water-soluble surfactants.

For approximately the past two decades, alkylbenzene sulfonates have been extensively used in synthetic detergent compositions. At present, the bulk of the commercial detergent compositions are based on this type of surfactant. The alkylbenzene sulfonate most generally employed in such compositions is dodecylbenzene sulfonate, obtained by alkylating benzene with a tetramer of propylene followed by sulfonating the alkylate and thereupon neutralizing the resultant sulfonic acid derivative. As a water-soluble surfactant for general household cleansing applications, dodecylbenzene sulfonate manifests excellent all-around properties. However, it nonetheless possesses a notoriously deficient property, namely, that of being extremely resistant to biodegradation. Consequently, considerable investigation has been directed of late to the development of surfactants of the alkylbenzene sulfonate variety which can .be readily biodegraded.

A recently proposed method for preparing biologically soft alkylbenzene sulfonates involves initially converting a straight-chain paraffin of the so-called detergent range or mixtures thereof into an alkylatable derivative. Thereupon, benzene is alkylated with said derivative to yield an alkylate whose monosulfonate salt exhibits detersive properties similar to the bio-resistant propylene tetramer derived substances. A suitable, and perhaps best manner from an economical standpoint for converting the straight-chain paraifin into an alkylatable derivative is to form the monochloride thereof. This can be achieved to a reasonable degree by partially chlorinating the paraffin or mixture of paraffins. In such a procedure, it would be desirable, as indicated, to form only monochloroalkanes. However, it is not known how to limit the introduction of only one atom into one molecule of the 'alkane in a chlorination procedure of this type and yet convert a substantial portion of the alkanes present. For example, upon the reaction of only two-tenths of an atom of chlorine per mole of alkane present, the resultant chlorination product, that is, the alkanes reacted, will be composed of about 90 percent monochloroalkanes and the balance essentially dichloroalkanes. Moreover, as the extent of chlorination is increased, the selectivity with respect to formation of monochloroalkanes will decrease. Since the mono-, dichloroand unreacted alkanes cannot be readily separated from one another, the total chlorination product must be used in the alkylation step. Thus, severe processing problems are encountered in the alkylation step if the initial chlorination is limited to the extent whereby essentially only monochloroalkanes are formed.

Originally, it was thought that the presence of dichloroalkanes would disadvantageously result in the formation of diphenylalkanes which have no value as surfactant precursors. However, it was found that a substantial portion of the dichloride content of the chlorination product when reacted with benzene results in the formation of alkyl tetralins and indanes. Furthermore, it was ascer- 3,272,81 Patented Sept. 13, 1966 tained that these particular polycyclic alkylates fortuitously yielded monosulfonate salts having acceptable detersive qualities and biodegradability properties.

Another by-product obtained in preparing biologically soft alkylbenzenes in accordance with a general procedure discussed are dialkylbenzenes. Perhaps it is significant to mention here that this by-product is also formed in the process of preparing alkylbenzenes via the use of propylene tetramers. The dialkylbenzenes obtained in the practice of the instantly considered method of preparing biodegradable alkylates unlike the diphenylalkanes are very valuable by-products as they can be readily converted into oil-soluble sulfonates. In this re gard, the particular type of dialkylbenzeues resulting from the use of propylene tetramer as the alkylating agent are decidedly refractory in this regard.

The method for manufacturing biologically soft detergent alkylates by the method generally described hereinabove is substantially more costlier than the method involved in preparing the counterpart bio-resistant alkylates. Consequently, it has become necessary for the potential manufacturer of biologically soft n-alkylben zenes to carefully scrutinize the process for the preparation thereof in order to effect economies. We have by the present invention provided such an improvement. More specifically, we have a way for converting the relatively useless by-product formed in this process, namely, diphenylalkanes, into commercially useful substances. In accordance with our novel improvement, the diphenylalkanes formed in the above-described process for preparing detergent alkylates are converted into polycyclic compounds corresponding to various 1,2,3,4-tetrahydronaphthylenes and indanes. These useful detergent precursors are readily obtained by reacting the diphenylalkanes by-product with aluminum chloride. Before discussing more specifically how our improvement can be carried out and the precise nature of the advantages realized in the practice thereof, it would be desirable first to particularize the process to which our invention is applicable.

In the preparation of biodegradable n-alkylbenzenes, the first step called for is the obtaining of a suitable alkane or mixture of alkanes which ultimately constitute the alkyl moiety of the alkylate. Suitable among such alkanes are the straight-chain paraffins of C -C carbon atom lengths which are abundantly available as components in various virgin petroleum fractions such as, for example, kerosene. Mixtures composed of these alkanes can be readily segregated from kerosene by either the well known molecular sieve or urea adduction methods. The art is replete on these techniques and consequently, no further details concerning same will be given herein.

After suitably segregating a fraction of normal paraffins 'within the stated detergent range, it is desirable to further fractionate same so as to obtain a mixture of normal paraflins wherein the difference in carbon atom length between the lowest and highest molecular weight member present does not exceed four carbon atoms. The reason for this is so that the resultant detergent alkylate can be recovered in a relatively pure state from the :alkylation reaction mixture inasmuch as adjacent higher alkanes boil within the range of the formed alkylates.

After the selected alkane or mixture thereof is obtained, it is then chlorinated. Either conventional liquid or vapor phase chlorination is applicable. The amount of chlorine reacted with the paraffin or mixture thereof can be within the range of from about 0.1-0.8 atom per molecule of paraffin present. More preferably, the degree of chlorination of the alkane is kept at less than about 40 mole percent, i.e., 0.4 or less atom of chlorine per molecule of paraffin.

Where liquid phase chlorination is observed, applicable temperatures range from about room temperature to 200 C. The preferred chlorination temperature for such a procedure is in the order of about 100150 C. With photochemical or other catalysis, lower temperatures can be used with the realization of good reaction rates. For the vapor phase method, thermal chlorination temperatures of 230370 C. are operable, although it is preferred to use a temperature within the range of 240- 260 C.

As mentioned previously, it is not feasible to separate the chloroalkanes from the unreacted alkanes. Consequently, it is a practical requirement that the total chlorination product be employed as the alkylatable component in the subsequent alkylation step. In the latter step, a wide range of benzene to chloropar-aflin molar ratios can be used such as, for example, from about 1:1 to 15:1, respectively. More preferably, the molar ratio of benzene to chloroparaflins is from about 5:1 to :1, respectively.

While any of the Friedel-Crafts catalyst can be used to facilitate alkylation of benzene with the chloroparaffins, aluminum chloride is preferred for the reason that it provides very rapid alkylation rates. Applicable amounts of aluminum chloride can range between about 1 and 10 percent based on the amount of chloroparaffins present in the alkylation reaction mixture. The preferred manner of supplying the aluminum chloride catalyst to the reaction system consists of enriching a catalyst sludge obtained from a previous alkylation run with a sufficient quantity of finely divided metallic aluminum to effect in situ formation of aluminum chloride during the course of the alkylation reaction.

The alkylation reaction can be carried out at a temperature of from about room temperature to 80 C. A preferred temperature range is in the order of from about 60-70 C. Employing a temperature within the preferred range, effective reaction time is in the order of about -60 minutes. The precise time needed for conducting the alkylation reaction is obviously dependent upon a host of factors including amount of catalyst used, ratio of benzene to alkyl chloride employed, temperature, etc.

Following the alkylation reaction, the effluent is introduced into a separator where the spent catalyst and sludge products are removed. The resulting effluent is then generally treated to remove acidic components. This can be readily accomplished by successively treating with sulfuric acid and caustic solution washings. After preliminarily treating the alkylation reaction effluent in the manner indicated, it is then fractionally distilled. Successive fractions of recycle benzene, recycle normal paraffins, alkylate products including alkylbenzenes and other polycyclic alkylates falling within the alkylbenzene boiling range, and a bottoms fraction essentially composed of diphenylalkanes and dialkylbenzenes are recovered in this manner.

The practice of the method of this invention can be accomplished in two principal ways. In one mode the bottoms fraction mentioned above, composed principally of a mixture of diphenylalkanes and dialkylbenzenes, can be reacted directly with aluminum chloride. Proceeding in this manner, the amount of aluminum chloride applicable ranges between about 5 and percent based upon the weight of the bottoms fraction. Suitable temperatures for effecting the conversion of the diphenylalkanes present are from 40-150 C. A more preferable range is from about 5080 C. The reaction is carried out until the rate of conversion of the diphenylalkanes into lower boiling monophenylalkylates substantially subsides. The progress of the conversion reaction can be readily followed by Gas Phase Chromatography (GPC) analysis. The advantage of reacting the bottoms fraction in the manner outlined resides in that the triand higher phenylalkane content thereof can be similarily converted into monophenylalkylates having usefulness as detergent substances.

An alternate procedure consists of first recovering the diphenylalkanes present in the bottoms fraction. This can be easily accomplished inasmuch as the dialkylbenzenes and higher polyphenylalkanes boil at a substantially higher temperature than do the diphenylalkanes. Upon reacting the diphenylalkanes obtained in this manner, effective conversion can be secured using lesser quantities of aluminum chloride than is the case when the bottoms fraction is treated in toto. In such an embodiment of our process, the amount of aluminum chloride is from about 5-15 percent based upon the weight of the diphenylalkanes so treated. Applicable reaction temperature ranges including the preferred range correspond identically to that given above for treating the total bottoms fraction.

In order to illustrate further this invention, the following working examples are set forth in which all parts are parts by weight unless otherwise specified. As mentioned, these examples are given primarily for the purpose of illustration and accordingly, any enumeration of details contained therein is not to be interpreted as a limitation on the invention except as indicated in the appended claims.

EXAMPLE I A kerosene cut having a boiling point range of from 398-520 F. was urea adducted in a conventional manner. The normal paraffins so segregated were then fractionally distilled to yield a mixture of C -C normal parafiins. Next, this mixture was chlorinated in liquid phase at a temperature between 70-110" C. for a period of approximately 20 minutes. The amount of chlorine reacted in this manner was 4 percent based upon the weight of the paraffin mixture. This represented a degree of chlorination of 20 mole percent. Following chlorination, the product was purged with inert gas in order to remove traces of unreacted chlorine and HCl formed during the course of reaction.

Benzene was alkylated with the chlorination product described above in the presence of 4 percent aluminum chloride based upon the chloroparaffin content of the chlonination product. A mole ratio of benzene to chloroparaifins of 10:1 was employed. The alkylation conditions consisted of stirring the reaction mixture for a period of approximately minutes while maintaining a temperature of 65 C. throughout the reaction. Following alkylation, the crude alkylate was settled to remove sludge and thereupon washed with '6 percent of concentrated sulfuric acid followed by a 20 volume percent washing of 5 percent sodium hydroxide. Following this purification procedure, the efliuent was then fractionated. The unreacted benzene was first distilled at atmospheric pressure. Next, the unreacted parafiins were recovered following which a detergent alkylate fraction boiling within the range of between 168 and 235 C. at 20 mm. Hg was recovered, thus leaving a bottoms fraction essentially composed of diphenylalkanes and dialkylbenzene.

A portion of the bottoms fraction was treated with increasing amounts of aluminum chloride at 60 C. with stirring. After the indicated intervals of time set forth in Table I hereinbelow, a sample was withdrawn, washed with water and analyzed by means of Gas Phase Chromatography. This analysis procedure permitted determination of the amounts present in the bottoms of the following components:

cluster of peaks associated with the component dialkylphenyls and consequently, are reported as a minor constituent of said component.

The results obtained in this experiment together with the specific reaction conditions observed are as follows:

chloride with stirring for one hour at 60 C. The reaction product (373 parts) was separated from the sludge,

To clarify the above data, it is specifically pointed out that successive additions of aluminum chloride were added to the same bottoms sample after which the sample was further heated for the additional time indicated. For example, Sample No. 3 represented a treated sample which had been heated for three hours in the presence of 2 percent aluminum chloride whereupon additional 4 percent of aluminum chloride was added and the sample further heated for an additional two hours.

These results show that the conversion rate of diphenylalkanes into monophenylalkylates is a function both of the amount of aluminum chloride used and the extent of the reaction time. These data also show that it is possible to convert triand higher phenylalkanes but that in order to do so relatively more severe reaction conditions are necessary.

EXAMPLE II A portion of the alkylate bottoms of Example I was treated with 25 weight percent of aluminum chloride for two hours at 60 C. The GPC analysis of the reaction products indicated the following composition:

Component A43.2 weight percent Component B12.5 weight percent Component C-44.3 weight percent EXAMPLE ill-I Table 11 Component Component Component Bottoms as is 43.1 50.1 6.8 After 2 hrs 32. 9 12. 1 55.0 After 3 hrs 32. 2 15. 7 52. 1

EXAMPLE IV The alkylate bottoms of Example I in the amount of 608 parts were reacted with 121.6 parts of aluminum 1.; washed with concentrated sulfuric acid and 10 percent sodium hydroxide solution in that order and distilled. The following cuts were obtained at mm. pressure.

Weight percent Cut #2 was sulfonated. The combining weight of the sodium sulfonate was determined to be 340 which indicated the material to be of the monophenylalkane type.

What is claimed is:

1. A method for converting polyph-enylalkanes present in a bottoms fraction obtained as a by-product in alkylating benzene with a chlorination product of from 0.1-0.8 atom of chlorine per mole of an alkane selected from the group consisting of C -C normal parafiins and mixtures thereof, into detergent grade polycyclic compounds boiling in the range from about 570-725 F., which comprises reacting said bottoms fraction with aluminum chloride at a temperature between about and 150 C.

2. A method in accordance with claim 1 wherein the amount of aluminum chloride is between about 5 and 25 percent based upon the weight of said bottoms fraction.

3. A method in accordance with claim 2 wherein said bottoms fraction is reacted with the aluminum chloride at a temperature between about and C.

4. A method in accordance with claim 1 wherein said bottoms fraction is first distilled to yield a distillate consisting essentially of diphenylalkanes and thereupon reacting said distillate with aluminum chloride.

5. A method in accordance with claim 4 wherein the amount of aluminum chloride is between about 5 and 15 percent based upon the weight of said distillate.

6. A method in accordance with claim 5 wherein said distill-ate is reacted With the aluminum chloride at a tem- 55 perature between about 40 and C.

References Cited by the Examiner UNITED STATES PATENTS 0 2,308,415 1/1943 Dreisbach 260668 DELBERT E. GANTZ, Primary Examiner.

C. R. DAVIS, Assistant Examiner. 

1. A METHOD FOR CONVERTING POLYPHENYLALKANES PRESENT IN A BOTTOMS FRACTION OBTAINED AT A BY-PRODUCT IN ALKYLATING BENZENE WITH A CHLORINATION PRODUCT OF FROM 0.1-0.8 ATOM OF CHLORINE PER MOLE OF AN ALKANE SELECTED FROM THE GROUP CONSISTING OF C10-C16 NORMAL PARAFFINS AND MIXTURES THEREOF, INTO DETERGENT GRADE POLYCYCLIC COMPOUNDS BOILING IN THE RANGE FROM ABOUT 570-725*F., WHICH COMPRISES REACTING SAID BOTTOMS FRACTION WITH ALUMINUM CHLORIDE AT A TEMPERATURE BETWEEN ABOUT 40 AND 150*C. 